Drafting instrument

ABSTRACT

A dial drafting device having a friction drive connection between a transfer wheel and an indexing plate. The drive ratio between the wheel and the plate can be carefully controlled by driving the plate with a beveled friction surface on the wheel. The plate receives calibrated discs for use in moving the device by an accurate spacing. Blank discs can be used for special programming.

United States Patent 11 1 11 1 1 De Mathe [4 1 Apr. 10, 1973 [54] DRAFIING INSTRUMENT FOREIGN PATENTS OR APPLICATIONS [75] Inventor? Leslie De Mathe, Buena Park, 721,845 1 1955 Great Britain ..33 109 Calif- 971,072 0/1950 France ..33/110 [73] Assignee: Stanley J. Adler, Culver City, Calif.

[22] Filed: Oct. 23, 1970 Primary Examiner-Harry N. Haroian Att0rney-Allen E. Botney [21] Appl. No.: 83,320

[57] ABSTRACT (g! A dial drafting devics having a friction drive connec Fie'ld 109 110 tion between a transfer wheel and an indexing plate. u The drive ratio between the wheel and the plate can 5 References Cited be carefully controlled by driving the plate with a beveled friction surface on the wheel. The plate UNITED STATES PATENTS receives calibrated discs for use in moving the device 287,200 10/1883 Wachs ..33 109 y an at sp i g. lank dis s can e us d for 1,051,712 1/1913 Eager special programming. 2,689,404 9/1954 Norman...

112,406 3/1971 B311 "I: ..33 109 6Clailm,7DrawingFigures PAM-Hm APR 1 0 mm LOGARlTHMlC ICYCLE PER I0 m INVENTOR. 4551/5 L. 05/144245 y E 5 w m wsm km 1T MM 5 DRAFTING INSTRUMENT This invention relates to a portable drafting instrument for use in technical designing and more particularly is directed to a dial drafting device.

Most existing drafting instruments require the use of a drafting table or drafting board for accuracy in completing technical drawings. Those instruments which have been designed for use on only a desk top are limited by inaccuracies due to the manner of construction of the instruments. Additionally, such. drafting instruments are normally incapable of providing means for accurately drawing angles, computing distances, dividing circles into segments or constructing geometric designs.

Many of the existing drafting devices are limited by the gear mechanism which becomes inefficient due to dust particles, or pencil erasures or other such materials which may alter the gear ratios by only a slight amount, but enough to make the instrument too inaccurate for use in technical drafting.

The dial drafting device of this invention includes transfer members for translating the device housing through a distance. The transfer members are drivingly connected to a display member to indicate the translational distance with. reference to. a fixed. index on the housing for the device. The display member in the preferred. embodiment is a calibrated disc removably mounted on a circular plate which is drivingly connected to one of the transfer members. The drive ratio between the transfer member and the plate issuch that a translation of the device. linearly by 1 inch (or any other. calibration):can beaccurately readonthe disc..

The device may include abraking mechanism for accurate positioning thereof-A center point defining pin for use in conjunction with a disc graduatedin .degreesmay be included. Preferably for high accuracy. the transfer member which drives the plate is a wheel providedwith.

an annular beveled circumferential resilient. ring. The plate is provided with a sharp annular depending ridge for riding on the beveled surface of the ring and adjustment screws are provided for varying the portion of the beveled surface contacted by the ridge to therebyvary the wheel diameter driving the plate and the drive ratio between the wheel and the plate.

A feature of the drafting instrument of this invention is that it performs without the need fora drafting table or board and can be used on loose sheets on a desk top.

Another feature of the instrument of this invention is that it includes a double dial which reads linear measurements including logarithmic spacing and angular degree settings.

Still another feature of the dial drafter of this invention is that it I computes distances between points at which lines are to be drawn by automatically adding or subtracting given distances including fractions and translates linear measurements to circumferential divisions on circles.

Another feature of the instrumentis .that dial discs with. stored memory can be placed on .theinstrument for determining stored linear design or spacing.

Another feature of the dialdraftingdevice of .thisinvention is that it is small, portable, simpleandsturdy in construction and includes .no complex gear systems which could .become jammed by dust or materials present on the drafting paper.

discussion of the invention when taken in conjunction with the appended claims and accompanying drawings wherein:

FIG. 1 is a top view of a dial drafting device con structed in accordance with this invention;

FIG. 2 is a longitudinal, vertical, sectional view through the dial drafting device of FIG. 1 taken substantially along line 2-2;

FIG. 3 is an enlarged partial sectional view showing the frictional connection between the drive wheel and the plate;

FIG. 4 is an enlarged view of the brake mechanism of the dial drafting device of FIG. 2 showing the brake in a released position;

FIG. 5 is an enlarged view of the center point pin mechanism of FIG. 2 showing it actuated for use in computing angular measurements;

FIG. 6 is a bottom plan view of a portion of the pivot point mechanism of FIG. 5; and

FIG. 7 is a plan view of a typical programmed dial disc for use with the drafting device of this invention.

Referring now to FIG. 1 itwillbe seen that the device of this invention comprises basically a longitudinal housing 10 which has a pair of mounting screws 12 for attaching an appropriate straight edge or scale 14 thereto. The scale has its zero position at the left end of the housing 10. The housing 10 includes a dial drafting disc vertically extending support rod 16 for rotatably mounting a circular dial drafting plate 18 which may receive a disc 20thereon and a central smaller diameter disc 20' thereon for rotation with the plate 18. The discs 20 and 20' may for example be graduated in inches or degrees or some other dimensions as will be explained. A weighted member such as the domed nut 22:may be used to hold thediscs 20 and 20' in place. The dome nut 22 may include magnets mounted in the lower surface thereof or may itself be magnetic to cooperate with the plate 18 if it is magnetic. If the plate 18 is not magnetic, a magnetic metal I washer (not shown) may be mounted in the plate immediately below the lower surface of the dome nut. This increases the ability of the dome nut 22 to hold the discs in place. Anyother manner of enhancing the attraction between thedome nut 22 and the plate 18 to fix the calibrated or blank discs in place can also be used.

The mounting screws 12 are removable so that the scale l4 can be replaced by any other type of drawing instrument. For example, a lay out scale which may have a slot for holdingthe drawing; pencil in place may be used. This can be used to combine vertical and horizontal movements of the drafting device to form a continuous line on thepaper.

The housing 10 also includes apair of transversely spaced brackets 24 adjacent the edge of theplate 18 which mount an indexing member 26. The indexing member 26, as shown in FIG. 2, is of substantially L- shaped cross-sectional configuration with the shorter leg of the L" extending into slots in the brackets 24. The brackets 24 are so spaced that a central indexing line 28 drawn or molded on the indexing member 26 coincides with a radius of the plate 18 and the disc 20. One of the side edges 30 of the indexing member 26 is inclined with the indexing line 28 so that it also coincides with a radius of the plate 18 and the disc 20. Thus, if both the indexing line 28 and the edge 30 were extended they would intersect the center point of the circular plate 18 and the disc 20. The usefulness of this arrangement of the indexing member 26 will become more apparent upon description of the operation of the drafting instrument of this invention. The housing also has a brake member 34 mounted thereon and an angular measurement adjusting pin assembly 36 mounted at the end opposite from the rod 16. A steadying tab 38 may be provided on one side of the drafting device for assistance in using the device. The draftsman may rest his little finger on the tab 38 and tilt the front edge of the scale 14 up to facilitate movement of the device.

Referring now to FIG. 2, it will be seen that the plate 18 is provided with an annular depending projection 40 which terminates in a sharp downwardly extending annular ridge 42. The housing 10 is provided with brackets 44 and 46 for mounting a pair of knurled wheels 48 and 50 which are rigidly connected to a longitudinally extending axle 52 so that both wheels rotate with the axle 52. The wheel 50 is connected to the axle 52, as shown in FIG. 2, by means of an integral wheel hub 51 that is press fitted onto the axle. As shown in FIG. 5, a coil spring 53 is fitted in an axial bore in the wheel 50 and abuts against the axle 52 and a stub shaft 55 to eliminate play in the wheels causes by side-to-side slippage of the axle. The left end of the axle 52 is journaled in the bracket 44 and the right end in the hub 51 for rotation therein. The stub shaft 55 is mounted in the bracket 46. The housing 10 and the brackets thereon are preferably integrally molded from a plastic material such as polycarbonate, polyethylene, polypropylene. The wheels are a metal such as aluminum or steel.

The wheel 48, as best shown in FIG. 3, is provided with a conical circumferentially extending groove which retains a resilient friction band such as the rubber band 56 therein. The friction band 56 is triangular in cross-section to match the shape of the groove in the wheel 48. The outer edge of the wheel 48 projects through an opening in the housing 10 slightly above the upper surface of the housing so that the ridge 42 of the plate 18 engages the friction band 56 to provide positive frictional connection between the wheel 48 and the circular plate 18. This friction bearing coordinates movement of the wheels and the plate 18. A magnet 60 is mounted on the housing 10 adjacent the wheel 48 beneath the plate 18 so as to stabilize the plate and bias it downwardly into contact with the friction band 56. The plate 18 is also preferably a heavy metal so that gravity biases it downwardly.

FIG. 3 shows more clearly the manner in which the friction band 56 engages the ridge 42 on the plate 18 so that the plate 18 rotates with the wheel 48. It is also shown that the drive ratio can be changed by adjusting the point at which the ridge 42 engages the friction band 56. For this purpose the friction band 56 is shown to have a beveled surface 57 which is produced by the use of a triangular sectioned rubber ring. The point of contact is adjusted by loosening a set screw 58 which engages a flattened portion 59 of the axle 52 and moving the wheel 48 either to the right or to the left. By adjusting the position of the wheel 48 by a minor amount highly accurate drive ratios can be obtained by the drive wheel 48 and the plate 18. In the preferred embodiment the ratio is 3 to 1, i.e. the drive wheel 48 revolves three times for every one revolution of the plate 18. The beveled surface 57 changes the diameter of the portion of the wheel 48 which drives the plate 18, thereby either increasing or decreasing the diameter and changing the drive ratio by a small amount to accurately maintain the preferred ratio for all instruments. With this finite adjustment any minor errors due to machining of the wheels can be corrected for improving the degree of accuracy of the drafting instrument. The annular ridge 42 may be serrated or grooved to enhance the frictional engagement of the ridge with the friction band 56 on the wheel 48. It has been found that thirty serrations or grooves per inch on the ridge 42 provide extremely adequate gripping of the ridge on the band.

If the plate 18 is nonmagnetic, such as a zinc plate, an annular strip of magnetic material may be provided on the lower surface thereof so that it extends annularly above the magnet 60 as the plate rotates about the rod 16. The plate may also be provided with a central Teflon (polytetrafluoroethylene) bushing which receives the rod 16 in a frictionless manner and permits easy rotation of the plate on the drive. As best shown in FIG. 2, the rod 16 is nonrotatably mounted in a bracket 62 on the housing 10. A small roller such as roller 61 may be mounted on an appropriate axle 63 for enhancing movement of the drafting device over surfaces which are not perfectly perfectly smooth. The ends of the axle 63 are mounted on appropriate integrally molded sockets in the housing 10 to permit rotation of the roller 61. Roller 61 has a smooth cylindrical side wall rather thanbeing knurled as are the wheels 48 and 50.

With continued reference to FIGS. 2 and with reference to FIGS. 4 and 5, the operation of the brake mechanism of the device of this invention will now be discussed. The brake mechanism 34 includes a pivotal brake arm 68 which pivots about a pair of pivot points defined by depending arms 70 which are notched at their lower end for passing through holes in the housing 10 so that they are nonremovably mounted thereto. Once the notched portion of the pivot tabs 70 is passed through the hole in the housing 10 it is twisted so that it cannot be removed with an instrument for twisting it back into the original configuration. The lower surfaces of the tabs 70 define a pivot axis. The lever 68 is attached at one end to a biasing means, such as the helical spring 72, which biases the left end of the brake arm 68 upwardly. A tab 74 at the left end of the brake arm 68 depends through a slot in the housing 10 for movement therethrough. In the normally upwardly biasing position, the opposite end (right end) of the brake arm 68 is pivoted downwardly so that a resilient braking pad 76, which is bonded to the brake arm 68, comes into contact with the knurled wheel 50 to provide a positive braking action on the wheel. The braking pad 76 may be any resilient material such as a polystyrene or foam rubber pad or other such resilient frictionally engageable member which is mounted on the metallic brake arm 68. A second magnet 78 is mounted on the housing so that it extends just below the extreme right end of the magnetic brake arm 68 downwardly supplementing the upwardly biasing force of the spring 72 acting on the opposite end of the brake and thereby enhancing the braking effect of pad 76 on the wheel 50. As shown in FIG. 4, when a force is applied to the left end of the brake lever arm 68, the lever pivots about the pivot axis defined by tabs 70 moving the frictional braking pad 76 out of contact with the wheel 50 to free the wheel for rotation and to enable movement of the drafting device.

As shown in FIGS. 2 and 4, the annular measurement adjusting pin assembly 36 comprises a bolt 80 which passes through a threaded orifice in the housing so that its lower end 82 engages the upper end of a resilient plate 84, which is mounted as by screws to the bracket 46 integrally molded on the housing 10. The plate 84, as best shown in FIG. 6, is provided with a slot 88 which receives a pivot pin 90 therein. Thus the pivot pin 90 is adjustable in the slot 88. To rotate the drafting device through a selected angle, the bolt 80 is advanced downwardly, into the position shown in FIG. 5, causing the pin 90 to engage the paper and lift the wheel 50 slightly off the paper. The pin 90 in this position acts as a center point for rotation of the drafting device through an angle which can be read on the disc mounted on the plate 18.

The operation of the device for drawing a series of equal spaced parallel lines will now be explained. The straight edge 14 is used for drawing the initial reference line. For example, a series of lines spaced 1 inch apart are to be drawn starting with the reference line. First a disc appropriately graduated in inches is placed on the plate 18. A nut or. other member can be placed on top of the disc to maintain it on position on the plate 18. The brake mechanism 34 is released by depressing the left end of the brake arm 68 as shown in FIG. 4. This frees the wheel 50 for rotation and enables rotation of wheel 48 through connecting axle 52. The rotation of the wheel 48, due to the positive frictional engagement of the ridge 40 with the friction band 56 on the wheel 48 and the interaction of the magnet 60 with the plate 18 or a metallic strip thereon, causes the disc 20 to be rotated when the drafting device is advanced. The disc is graduated depending on the drive ratio between the wheel 48 and the plate 18 so that the plate revolves through a 1 inch division when the wheels 48 and 50 move linearly 1 inch. The index line 28 is used to determine the distance by which the drafting device is advanced by accurately correlating plate rotation to the graduations on the disc 20. Thus for 1 inch spacing, the drafting device is moved forward on the wheels 48 and 50 so that the disc 20 rotates through a 1 inch. graduation under the index line 28. Since the wheels 48 and 50. are knurled and positively connected. by the axle 52 and since a downward pressure has to be applied to the brake mechanism 34 in order to enable any movement of the drafting device, the advancement will be in a direction parallel to the first line and thus a second line can be drawn using a straight edge 1 inch from the first line. The second line is automatically parallel to the first. In this manner a series of parallel lines spaced by whatever distance is desired based on the dial readings can be drawn.

For use of this device for drawing lines at predetermined angles from a fixed reference line, the reference line is first drawn using the straight edge 14, then the bolt is threadedly advanced downwardly causing the center point pin to contact the sheet of paper on which the drawing is made. This lifts the wheel 50 off the paper. Another disc 20 which is graduated in degrees is placed on the plate 18 or as shown in FIG. 1 a smaller diameter disc 20 which is graduated in degrees may be placed on top of the larger disc 20. The brake lever 68 is then depressed freeing the wheel 50 and the wheel 48 for rotation. The instrument is then rotated about the central point 90 causing rotation of the disc 20 or 20' in the manner discussed previously with the wheel 48. When the disc rotates through the desired number of degrees as read] by the index line 28 the brake lever is released and the straight edge is used for drawing a line which makes the desired predetermined angle with the reference line.

In the foregoing manner the simple operations of drawing accurately spaced parallel lines or lines displaced at an angle from one another can be accomplished. The device is further diverse, however, in that it can be used for plotting logarithmic spacing on graph paper by using a disc 20, such as shown in FIG. 7 which is graduated in a logarithmic scale. Additionally the device may be used for accurately drawing measure ments which are divided into l/16 inch or 1/32 inch divisions or accurate divisions which include ten divisions per inch or twenty divisions per inch. The device may also be used with an appropriate disc 20 to accurately scale a drawing at one-fourth inch equals 1 foot or any other scale programmed on an appropriate disc. It has been found that graduations of one-half of a degree can accurately be drawn using the device of this invention.

By the use ofa blank uncalibrated disc like disc 20, it has been found possible to lift spacings from one set of drawings to another in a very accurate manner. If a bland disc 20 is properly positioned on the plate 18, the drafting device may be used to store the spacing between a series oflines on a document. This is done by placing the straight edge in alignment with each line and by using the indexing edge 30 to draw a straight line on the disc corresponding to each line on the document. In this fashion the disc is programmed so that those spacings can be accurately transferred to any drawing sheet for which such spacing is desired.

It has also been found that with the dial drafting device of this invention it is a simple operation to divide a circle into any desired number of parts. This is accomplished by using a blank dial disc of a standard circumference such as the disc 20. Suppose that a disc having 10 inch circumference is used and that a circle is desired to be divided into 10 equal segments. The drafting device is simply placed on a linear divided scale 10 inches long and divided into ten 1 inch segments. The straight edge is moved 1 inch at a time and the disc is appropriately marked along the indexing edge 30 for each 1 inch advancement of the drafting device.

After the disc has been so marked, it can be placed over a predrawn circle so that its center point corresponds with the center point of the predrawn circle. The lines marked on the blank disc 20 are extended to divide the predrawn circle (of any diameter) into 10 equal segments. In a similar manner a circle can be divided into 13, 360 or any other number of divisions by the use of an appropriate linear scale for programming the blank disc. The key to such divisions is the use of the indexing edge 30 which coincides with a radius of the disc.

The dial drafting instrument can be used to add or subtract distances without separately calculating the sum or difference by simply returning the dial to the zero position after moving each desired distance. The total movement is the sum or difference of all movements.

The multiple uses to which the dial drafting device of this invention can be put should be readily apparent from the few examples discussed herein. By the use of uncalibrated discs the draftsman can program the device by appropriately marking the disc to perform a great many drafting functions such as disecting angles, translating spacings from one document to another, translating graph paper divisions, providing mapping scales and the like.

Another advantage of the drafting device is that the scale 14 has its zero positioned at the left end of the housing 10 so that it is not necessary for the draftsman to cross hands in making a full scale line.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

1. A dial drafting device comprising:

a housing;

a pair of transfer members mounted on said housing for movement thereof, said transfer members being connected to each other for movement in unison, said transfer members respectively including a pair of wheels connected to a common axle for rotation therewith;

a braking member mounted on and above said housing and connected to one of said transfer members for positive engagement therewith to prevent movement thereof;

a display member for indicating the distance through which said housing is moved, said display member including a disc support member drivingly connected to the other of said transfer members, the wheel included in said other transfer member having frictional means mounted thereon to provide said driving connection with said disc support member, said frictional means including a groove circumferentially extending along the wheel and a resilient friction band mounted therein, said groove and friction band being adapted to provide a friction surface at an angle with the surface of said wheel, said disc support member including a generally circular plate having an annular drive member thereon for engaging said friction surface to positively connect said plate and said wheel;

adjustment means coupled to the wheel included in said other transfer member for varying the portion of said friction surface contacted by said annular drive member; and

a stationary indexing member mounted on said housing and extending above said disc support member to index movement of said disc with respect to movement of said device.

2. A device as defined in claim 1 wherein a portion of said plate is magnetic and a magnet is mounted on said housing below said portion of said plate to bias said drive member into contact with said frictional band.

3. A device as defined in claim 1 wherein said braking member comprises a brake arm mounted for movement about a pivotal axis and having a resilient high coefficient of friction member mounted thereon, said device including biasing means for biasing said friction member into contact with the wheel included in said one transfer member for preventing movement thereof 4. A device as defined in claim 3 wherein said friction member biasing means comprise: a spring mounted on one side of the pivotal axis of said brake arm and a magnet mounted on the housing at the opposite side of said pivotal axis, said friction member being mounted on the same side of the pivotal axis as said magnet so that said spring and said magnet bias the frictional member into contact with said one wheel by a force which can be overcome by pressing against the biasing effect of the spring.

5. A device as defined in claim 1 wherein said indexing member includes a line and an edge that coincide with first and second radii, respectively, of said disc support member.

6. A device as defined in claim 1 wherein said adjustment means includes a flattened portion of said axle that extends into said other wheel, and a set screw that abuts against said flattened portion. 

1. A dial drafting device comprising: a housing; a pair of transfer members mounted on said housing for movement thereof, said transfer members being connected to each other for movement in unison, said transfer members respectively including a pair of wheels connected to a common axle for rotation therewith; a braking member mounted on and above said housing and connected to one of said transfer members for positive engagement therewith to prevent movement thereof; a display member for indicating the distance through which said housing is moved, said display member including a disc suppOrt member drivingly connected to the other of said transfer members, the wheel included in said other transfer member having frictional means mounted thereon to provide said driving connection with said disc support member, said frictional means including a groove circumferentially extending along the wheel and a resilient friction band mounted therein, said groove and friction band being adapted to provide a friction surface at an angle with the surface of said wheel, said disc support member including a generally circular plate having an annular drive member thereon for engaging said friction surface to positively connect said plate and said wheel; adjustment means coupled to the wheel included in said other transfer member for varying the portion of said friction surface contacted by said annular drive member; and a stationary indexing member mounted on said housing and extending above said disc support member to index movement of said disc with respect to movement of said device.
 2. A device as defined in claim 1 wherein a portion of said plate is magnetic and a magnet is mounted on said housing below said portion of said plate to bias said drive member into contact with said frictional band.
 3. A device as defined in claim 1 wherein said braking member comprises a brake arm mounted for movement about a pivotal axis and having a resilient high coefficient of friction member mounted thereon, said device including biasing means for biasing said friction member into contact with the wheel included in said one transfer member for preventing movement thereof
 4. A device as defined in claim 3 wherein said friction member biasing means comprise: a spring mounted on one side of the pivotal axis of said brake arm and a magnet mounted on the housing at the opposite side of said pivotal axis, said friction member being mounted on the same side of the pivotal axis as said magnet so that said spring and said magnet bias the frictional member into contact with said one wheel by a force which can be overcome by pressing against the biasing effect of the spring.
 5. A device as defined in claim 1 wherein said indexing member includes a line and an edge that coincide with first and second radii, respectively, of said disc support member.
 6. A device as defined in claim 1 wherein said adjustment means includes a flattened portion of said axle that extends into said other wheel, and a set screw that abuts against said flattened portion. 